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參數(shù)資料
| 型號(hào)： | MAX2003A |
| 廠商： | Maxim Integrated Products, Inc. |
| 元件分類： | 基準(zhǔn)電壓源/電流源 |
| 英文描述： | Fast-Charge Battery Chargers(NICD/NIMH,可充電池?cái)?shù)1~16個(gè),電池快速充電器) |
| 中文描述： | 快速充電電池充電器（鎳鎘/鎳氫電池，可充電池?cái)?shù)1?16個(gè)，電池快速充電器） |
| 文件頁數(shù)： | 15/20頁 |
| 文件大?。?/td> | 191K |
| 代理商： | MAX2003A |
In order to provide high currents with minimum ripple,
the device must function in the continuous-conduction
mode. Figure 10 shows a current waveform of an
inductor in the continuous-conduction mode (where the
coil current never falls to zero).
The average load current (I
LOAD
) through the inductor
must be 1.7A, so a peak current (I
MAX
) of 1.9A should
give a fairly low ripple while keeping the inductor size
minimal. This means that the total current change (Figure
10) across the inductor is
δ
i = 2 (1.9 - 1.7) = 0.4A.
The maximum voltage across the inductor is present
when the battery voltage is at its minimum. The mini-
mum cell voltage at the start of fast-charge will be 1V
per cell, giving a battery voltage of 6V for 6 cells. The
maximum voltage (V
L
) across the inductor is therefore:
V
L
= (input voltage - minimum battery voltage)
The input voltage for this application is 13V, so the
maximum voltage is:
V
L
= (13V - 6V) = 7V
The minimum on-time
δ
t of the switch is given by:
δ
t = (V
OUT
/ V
IN
) x PERIOD
where V
OUT
is the minimum battery voltage, V
IN
is the
maximum input voltage, and PERIOD is the period of
the switching signal.
The maximum input voltage for this application will be
14V, and the maximum allowed switching frequency of
100kHz gives a period of 10μs. The minimum on-time
will therefore be:
δ
t = (V
OUT
/ V
IN
) x PERIOD = (6V / 13V) x 10μs = 4.62μs
The inductor value can be calculated from:
L = V
δ
t /
δ
i = (7V x 4.62μs) / 0.4A = 81μH.
If this inductor value is used, the actual switching fre-
quency will be lower than the 100kHz expected, due to
comparator delays and variations in the duty cycle. The
inductor value selected for our application will be
100μH—a preferred value just above the calculated
value. It is important to choose the saturation current
rating of the inductor to be a little higher than the peak
currents, to prevent the inductor from saturating during
operation. The inductor must be selected to ensure that
the switching frequency of the MOD pin will not exceed
the 100kHz maximum.
Additional Applic ations
_________________________Information
The MAX2003/MAX2003A can use several other cir-
cuits to charge batteries. Figure 9 shows a circuit that
uses a Darlington transistor to regulate the current a
six-cell NiCd battery pack receives. Figure 10 shows a
gated current-limited supply being used to charge a
Duracell NiMH battery pack. Table 6 lists the external
components used in these two application configura-
tions.
Linear Regulation of Charge Current
The circuit in Figure 11 uses an inexpensive transistor
to provide the charge current. Since the input for the
MAX667 can tolerate up to 16V, this circuit can charge
up to 7 cells. The MAX667 can be replaced with a dif-
ferent regulator if more cells need to be charged. The
DC source must supply a voltage equal to 2x the num-
ber of cells, plus 2V overhead to accommodate the
drop across external components.
When fast-charge is initiated, the voltage at the SNS pin
is sampled and compared to the trip levels (220mV low
and 250mV high). If the voltage at SNS is below
220mV, the MOD pin will switch high, and the 10k/1μF
RC lowpass filter will pull high, turning on the NPN tran-
sistor. This will pull the base of the Darlington TIP115
low, turning it on and allowing current to flow into the
battery. When the current through the battery and SNS
resistor are high enough, the voltage at SNS will
exceed 250mV and the MOD pin will turn off.
The amount of current the battery receives depends on
the resistor between SNS and V
SS
. In our example cir-
cuit, the average current through the SNS resistor will
be:
I
SNS(AVG)
= V
SNS(AVG)
/ R
SNS
= 0.235 / 0.28 = 0.84A
The maximum current the resistor will receive is:
I
SNS(MAX)
= V
SNS(MAX)
/ R
SNS
= 0.25 / 0.28 = 0.90A
The Darlington transistor must be biased to ensure that
a minimum of 0.90A will be supplied. This minimum
M
NiCd/NiMH Battery Fast-Charge Controllers
______________________________________________________________________________________
15
Table 6. External Component Sources
(602) 994-6430
(602) 303-5454
Motorola
Power
MOSFET &
Darlington
Transistor
(904) 462-4726
(203) 791-3273
(904) 462-3911
Energizer
Power
Systems
(800) 431-2658
Duracell
Battery
(619) 549-4791
(510) 460-5498
Fax Number
(800) 235-5445
Alpha
Thermistor
Thermistor
Device
(510) 734-3060
Advanced
Power
Solutions
Power
Supply
Phone
Number
Manufacturer
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| MAX2003AC/D | 制造商:MAXIM 制造商全稱:Maxim Integrated Products 功能描述:NiCd/NiMH Battery Fast-Charge Controllers |
| MAX2003ACPE | 制造商:Maxim Integrated Products 功能描述: |
| MAX2003ACSE | 制造商:Rochester Electronics LLC 功能描述: 制造商:Maxim Integrated Products 功能描述: |
| MAX2003ACWE | 制造商:MAXIM 制造商全稱:Maxim Integrated Products 功能描述:NiCd/NiMH Battery Fast-Charge Controllers |
| MAX2003ACWE+ | 制造商:Rochester Electronics LLC 功能描述: 制造商:Maxim Integrated Products 功能描述: |
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